This protocol results from a funded 2005 Bench-to-Bedside Award and explores the genetic basis of disease severity in neurofibromatosis type 1 (NF1) and the evaluation of three methods to measure disease progression of dermal neurofibromas. NF1 is a common multisystem genetic disorder associated with the development of benign and malignant tumors, primarily of the nervous system. NF1 is 100% penetrant and features variable expressivity and limited phenotype/genotype correlation. No standard treatment other than surgery exists for most NF1-associated tumors. Many aspects of the natural history of NF1-associated tumors